In recent years, instead of a conventionally used fluorescent light and the like, a light emitting diode (hereinafter referred to as LED) and a laser diode (hereinafter referred to as LD) consuming less electricity and having a longer service life and smaller size compared with the fluorescent light and the like have begun to be used as a light source for a surface illumination device such as a liquid crystal display backlight device.
For example, Patent Document 1 listed below describes an edge light type lighting device using an LED. The lighting device includes the LED, a light guide plate comparable in size to a post card and having a light guide portion for light from the LED formed as a flat surface, and a reflecting mirror that reflects light from the LED, and is configured in such a manner that the LED is mounted on the flat surface of the light guide plate and covered by the reflecting mirror. Patent Document 2 listed below describes a lighting device in which light from an LED is guided to a light guide plate through a light source rod including a prism array. Patent Document 3 listed below describes a cash register guide lamp in which a plurality of LEDs are disposed at equal intervals on a light input surface of a light guide body, light from the LEDs is irregularly reflected by a reflector body, and the diffused light makes a light output surface of the light guide body emit surface light to illuminate a display body opposed to the light output surface of the light guide body.
While the lighting devices described above are of the edge light type, a direct type lighting device is also known. For example, Patent Document 4 listed below describes a surface light emitting device in which an LED is provided with a light controller that controls light from the LED so that surface light can be obtained. Patent Document 5 listed below describes a surface lighting light source device and a surface illumination device using the surface lighting light source device. The surface lighting light source device includes: an LED; a box-shaped casing including a bottom surface portion in which the LED is mounted at the center portion and side surface portions standing from a periphery of the bottom surface portion, and being provided with an opening formed on a side opposite to the bottom surface portion; and an optical reflector plate that covers the opening and substantially uniformizes the light from the LED. The surface illumination device uses the plurality of surface lighting light source devices that are connected to each other.